This invention relates to a browning composition for foods having a dough crust. More particularly, the invention relates to a coating composition for foods having a pastry crust which undergoes browning reactions upon microwave or conventional heating to provide cooked products having a desirable browned crust.
The usage of microwave ovens in homes has increased significantly in recent years and continues to increase. While microwave cooking of foods affords a significant time saving over conventional convection oven cooking, it suffers from the disadvantage that foods cooked by microwave energy lack the desired degree of surface browning that foods, particularly those having a dough crust such as meat pies and fruit pies, have when cooked in a conventional oven.
The most common reaction responsible for surface browning during cooking of products having a dough crust is the well-known Maillard reaction (non enzymatic browning) between naturally occurring reducing sugars and compounds containing an amino group, e.g. amino acids, peptides and proteins, which results in the formation of colored melanoidins. The rate at which the Maillard reaction proceeds to form the colored pigments increases markedly with temperature. When foods containing a dough crust, such as frozen pies, are heated in a conventional oven, the crust is heated to considerably higher temperatures than the interior of the pie, with the high surface temperatures being sufficient to achieve browning. However, in microwave heating the heat energy is released internally within the food so that the surface remains at a relatively even temperature with the interior. Consequently the high surface temperatures necessary to achieve browning are not reached within the time required to bake the pie.
A number of compositions have been proposed heretofore to create a browned surface on foods heated by microwave energy. However, none of these prior compositions has been entirely satisfactory due to flavor concerns, cost, ineffectiveness, difficulty of use, and other problems.
According to the present invention, there is provided a browning composition comprising a caramel color and a thickening agent.
The preferred thickening agent is a modified starch and the caramel color is generally provided by a melanoidine. When the disclosed amounts and ratios of these additives are included in a dough crust and subjected to heating, the surface of the dough crust easily develops a browned surface condition without experiencing the difficulties of the prior art.
The pH of the browning composition is preferably less than 7 e.g. from 3 to 5.
The caramel color may be ordinary caramel colour or it may advantageously be a caramel color replacement. Examples of caramel color replacements are brown compounds which, based on limited solubility in both organic and aqueous solvents, appear to be classical melanoidines of unknown structure having an average molecular weight range of from 1 to 10 kDal. The melanoidines may be prepared by reacting a reducing sugar with a compound containing free amino groups such as an amino acid, peptide or protein. The sugar may be a currently available raw material such as glucose, fructose, galactose, lactose, dextrose (e.g. from corn syrup) or maltose. The compound containing free amino groups may be, for instance, ammonia, a hydrolysed plant protein, a yeast derivative such as a yeast autolysate or yeast extract, an oil cake of peanut or soya, gluten, casein or proteins of microorganisms.
The thickening agent may be for example a modified starch, a polysaccharide or a hydrocolloid gum such as carrageenan, locust bean, alginate or guar gum. Preferably, the thickening agent is also a stabiliser for storage at low pH, especially storage in a freezer and improves the freeze-thaw stability. The thickening agent helps to retain the browning composition on the surface of the dough crust when applied.
The ratio of caramel colour to the thickening agent may be from 5:100 to 100:100 and preferably from 10:100 to 50:100 by weight.
The browning composition may be used in the form of an aqueous emulsion or as a dry powder e.g. formed by spray drying or freeze-drying the emulsion.
When the browning composition is used in the form of an aqueous emulsion, the amount of caramel color is conveniently from 1 to 25%, preferably from about 2.5 to 20% and especially from about 5 to 15% by weight based on the total weight of the browning emulsion. The amount of water in the emulsion may be from about 50 to 90% by weight based on the total weight of the browning composition.
Advantageously an edible oil is present in the browning composition to aid heat transfer. Examples of oils are corn oil, soy oil, safflower oil, cottonseed oil and sunflower oil. The amount of oil present in the composition is advantageously 5 to 50 times the amount of caramel colour. An emulsion of the browning agent may contain from 5 to 50% by weight of edible oil based on the total weight of the emulsion. The presence of an edible oil may provide enhanced browning of the dough crust on microwave heating.
Other ingredients which may be present in the composition include food grade acids to provide acidity and give a longer shelf life, sugared egg yolk, a flavor such as paprika, or hydrolysed plant proteins.
The present invention also provides a process for treating a food product having a dough crust to render the crust brownable upon heating in a conventional or microwave oven which comprises applying to the surface of the dough crust an amount of a browning composition comprising a caramel color and a thickening agent effective to develop a browned surface on the crust when heated in a conventional or microwave oven.
The browning composition can be conveniently coated, such as by brushing, spraying, and the like onto the surface of a previously formed dough crust of a food to be baked, such as a meat pie or fruit pie. Satisfactory results are obtained when the composition is coated onto the surface of the dough crust in an amount of about 0.008 to 0.02 gm/sq. cm. The crust may be formed of any of the well known dough materials conventionally used in the preparation of crusts for frozen pies, such as flour, water, fat or shortening, as well as conventional additives for modifying flavor and/or texture. The coating composition may be applied to the dough crust at the time the pie is prepared after which the resulting product is frozen and maintained in a frozen state until baking. Alternatively, the coating composition may be applied to the dough surface after the pie has been frozen.
The food product having the dough crust which has been coated with the composition of this invention may be baked in a microwave oven utilizing conventional time-temperature relationships which will vary depending on the nature and size of the product. During microwave heating, the surface of the dough crust undergoes a browning reaction to provide a baked crust having a desirable golden brown appearance substantially the same as that obtained by baking the food product in a conventional convection oven.